The following list of applications for time-scaling audio signals can be found in Dorran et al., “A Comparison of Time-Domain Time-Scale Modification Algorithms,” AES 2006:                Fast browsing of speech material for digital libraries and distance learning        Music and foreign language learning/teaching        Fast/slow playback for telephone answering machines and Dictaphones        Video-cinema standards conversion        Audio Watermarking        Accelerated aural reading for the blind        Music composition        Audio-video synchronization        Audio data compression        Diagnosis of cardiac disorders        Editing audio/visual recordings for allocated timeslots within the radio/television industry        Voice gender conversion        Text-to-speech synthesis        Lip synchronization and voice dubbing        Prosody transplantation and karaoke        
A way of realizing such a digital signal processing technique for audio signal length change is the so-called Waveform Similarity OverLap Add (WSOLA) approach. WSOLA is capable of producing time scaled output signals of high quality. The WSOLA output signal is constructed from blocks of a fixed length (typically around 20 ms). These blocks overlap by 50% so that a fixed cross-fade length is guaranteed. The next block appended to the output signal is the one that is, first, most similar to the block that would normally follow the current block and that, second, lies within a search window around the ideal position (as determined by the scaling factor). The deviation from the ideal position is thereby typically restricted to be less than 5 ms resulting in a search window of 10 ms in size.
Demol et al. describe in, “Efficient Non-Uniform Time-Scaling of Speech with WSOLA,” Speech and Computers (SPECOM), 2005, that WSOLA may also be extended to take the varying characteristics of the processed signal into account for by varying the scaling factor.